A conventional spherical bearing is typically composed of three main components: a metal outer race, a polymeric low friction liner, and a metal spherical ball that travels along the outer race in contact with the liner. The liner is a composite material that is applied to the inner surface of the outer race in an uncured state, and is then dried, rolled and formed by curing on the inner surface of the outer race. The cured liner is designed to act as a self lubricating bearing surface.
A major manufacturing process for spherical bearing manufacturing includes the insertion of a pilot ball to apply pressure during curing to form the final interference fit between the outer race inner surface and the outer surface of the pilot ball.
Snapping and swaging represent the two predominant current methods for inserting the pilot ball into a spherical bearing. Snapping includes ovalizing the outer race to enable the insertion of the solid spherical pilot ball, while swaging includes pushing the solid spherical pilot ball into the outer race. Both of these methods require expensive equipment for the elastic or plastic deformation of the outer race. In addition, these conventional methods also require a large amount of deflection of the outer race. This deflection can cause the outer race to crack and to ultimately damage the bearing, to compromise the safety of the assembly operator. For instance, the snapping assembly method requires that the operator insert the pilot ball while the outer race is being ovalized by a large radial force. If the stored energy in the bearings outer race were released, and the ball is ejected from the cracked outer race, a fatal accident can ensue.
In addition to the safety and cost considerations, the yield of these two conventional assembly methods is not optimal, since excessive deflection of the outer race can cause some permanent distortion or an increase in the outer diameter to become larger than the pilot ball diameter. This frequently results in cracked outer races and scrapped bearings, after a significant amount of time and money have been invested in manufacturing and assembling the scrapped bearings.
Attempts have been made to improve the conventional assembly techniques by redesigning either the outer race or the liner, while retaining the integral spherical solid design of the pilot ball. Nonetheless, these attempts have not proven to be completely satisfactory.